1. Field of the Invention
The present invention is generally directed energy consumption in computer datacenters. More particularly, the present invention is directed to congestion sensing to reduce consumed energy in multiprocessor systems such as network datacenters.
2. Description of Related Art
Large scale computing systems often employ datacenters or server farms to support a variety of applications and services. Such datacenters and server farms may employ many servers to handle the processing load. Each server consumes a certain amount of power when executing operations, and a different amount of power when idle. The cost of supplying power and its associated delivery and cooling are significant factors in the total expenditures of large-scale datacenters.
Studies have shown that datacenter computers rarely operate at full utilization. However, known datacenter networks often exhibit very little dynamic range. That is, the power consumed when the network is idle is nearly the same as the power consumed when the network is fully utilized. A primary reason is that high-speed channels typically operate in an “always on” mode regardless of whether they are flowing data packets. Without a reactivation latency hit, the channels cannot be quickly deactivated and then reactivated without negotiation from both sides of the channel to establish data rate, symbol alignment, and lane alignment.
Further exacerbating the problem is that deactivating a link appears as if the link is faulty to the routing algorithm, in which case packets must either be buffered or routed around the deactivated link. Buffering for extended periods of time is not feasible, leading to packet discards or backpressure depending on the network's flow control mechanism. On the other hand, changing routes in many networks require coordination among all nodes to ensure that no newly injected traffic takes a path that would cross an inactive link.